Kata in Judo is essentially just practicing a single pre-determined throw or lock. Dangerous techniques, e.g. standing joint locks, punches and kicks which are banned in randori are still taught in kata. Also, Judo kata are very short, only a few movements ending with a throw, choke or joint lock.

There's really no need to imagine a partner since all kata are performed with a real partner (who usually take turns to perform techniques as Uke and Tori).